Cambodian opposition leader Sam Rainsy returned from overseas Saturday to be greeted by thousands of supporters, just days before the anniversary of last year's disputed general elections. He called for the release of detained opposition politicians and for talks to end the country's political deadlock.

Up to 20,000 cheering supporters were on hand to welcome Cambodian opposition leader Sam Rainsy on his return to Phnom Penh. He was transported by open top truck through the city.

Sam Rainsy's return comes just days after street clashes outside Freedom Park - which is closed off to rallies - later led to the arrest of seven member of his Cambodia National Rescue Party [CNRP].

In an address to his supporters Saturday, Sam Rainsy called on the government to once again allow freedom of speech.

Sam Rainsy also called for the detained politicians to be released and for Freedom Park to be reopened to allow people to rally.

Cambodia's political climate remains highly charged, almost a year after the disputed general elections nominally won by Prime Minister Hun Sen's ruling Cambodian People's Party [CPP] but disputed by the opposition and international observers.

Sam Rainsy's party has boycotted the National Assembly and is calling for reforms before new elections are held.

Political tensions have been rising over several months, with security forces cracking down on street protests that rights groups say have largely been peaceful.

Seven opposition lawmakers-elect were detained and now face charges ranging from insurrection to incitement to violence, carrying possible jail sentences of up to 30 years.

Andre Giorgetta, a spokesperson for the International Federation of Human Rights, said the violence reflects growing frustration within the opposition after attacks in the past by security forces.

"Our concern is the ongoing ban on peaceful assembly that is creating a situation that is very dangerous because a lot of people feel very frustrated and exasperated after months of demonstrations that have been repressed by the security forces, the security guards and sometimes even by hired thugs," he said.

On Saturday, opposition leader Sam Rainsy called for talks to end the political deadlock. He said the solution lies in peaceful negotiations in order to avert violence.

Rights groups have condemned the ongoing detention and charges against opposition members of parliament, saying the arrests will make it more difficult for a resolution of the political conflict.